Horizontal Articulated Robot Arm Layout to Eliminate Shaft Dead Zones

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Solution Overview

Problem

Existing horizontal articulated robots face limitations in securing a long working shaft due to interference and dead zones, restricting the vertical stroke and range of motion.

Innovation Solution

A horizontal articulated robot design with a first arm and second arm configuration where the first distance between the first and second axes of rotation is shorter than the second distance between the second and third axes, allowing the working shaft to protrude beyond the first arm and incorporate an offset member to reach the first axis of rotation, thereby preventing dead zones.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the first arm and second arm have approximately the same length to prevent working shaft interference, then the working shaft can be positioned safely, but the vertical stroke of the working shaft is restricted and lengthening of the working shaft is restricted

Engineering Contradiction:

Improveworking shaft interference preventionVSAvoidvertical stroke of working shaft

Core Design Contradiction:

ReliabilityVSLength of moving object

Solution Approach 1:

The patent applies asymmetry by making the second arm longer than the first arm. Specifically, the first distance (between first and second axes of rotation) is shorter than the second distance (between second and third axes of rotation). This asymmetric configuration allows the working shaft to extend vertically beyond the first arm without interfering with it, thereby resolving the contradiction between preventing interference and achieving sufficient vertical stroke.

Inventive Principle:

Principle #4Asymmetry

2Reliability

If the working shaft is kept below the lower surface of the first arm to avoid interference, then interference is prevented, but the range of motion is restricted due to dead zones

Engineering Contradiction:

Improveinterference preventionVSAvoidrange of motion

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The asymmetric arm configuration (second arm longer than first arm) enables the working shaft to protrude above the first arm's lower surface. This eliminates dead zones by allowing the working shaft to reach positions that would otherwise be inaccessible, thereby expanding the robot's range of motion while maintaining reliable operation without interference.

Inventive Principle:

Principle #4Asymmetry

3Device complexity

If a conventional SCARA robot configuration is used with equal arm lengths, then the structure is simple and stable, but a long working shaft cannot be secured without dead zones

Engineering Contradiction:

Improvearm configuration simplicityVSAvoidworking shaft length

Core Design Contradiction:

Device complexityVSLength of moving object

Solution Approach 1:

The patent modifies the conventional SCARA configuration by making the second arm longer than the first arm. This simple asymmetric modification allows the working shaft to be extended while maintaining structural stability and avoiding dead zones, achieving longer working shaft length without significantly increasing device complexity.

Inventive Principle:

Principle #4Asymmetry

Data Source

PatentUS12576512B2Horizontal articulated robot

Publication Date: 2026.03.17 FANUC LTD

AI summary

A robot (10) includes a fixed part (20), a first arm (21), a second arm (22), and a working shaft (25). The second arm (22) is longer than the first arm (21). A protrusion length of the working shaft (25), which is capable of protruding from the second arm (22) toward the fixed part (20) is longer than a distance between the first arm (21) and the second arm (22).